Indane compounds having negative dielectric anisotropy

ABSTRACT

The invention relates to indanes having negative Δε of the formula Ia or Ib  
                 
 
     in which R, A, Z, X, Y, V, W, n and m are as defined in claim 1.  
     The compounds are particularly suitable for producing VA-TFT displays.

[0001] The invention relates to indane compounds having negative Δε.

[0002] Liquid crystals have been widely used ever since the firstcommercially useful liquid-crystalline compounds were discovered 30years ago. Typical application areas are in particular displays forwatches and clocks or pocket calculators, or large display panels asused in stations, airports and sports arenas. Other application areasare displays of portable computers or navigation systems, and videoapplications. The latter applications in particular have to meet highrequirements on switching times and image contrast.

[0003] As a result of the spatial order of the molecules in a liquidcrystal, many of its properties are anisotropic. Of particularimportance for use in liquid-crystal displays are anisotropies inoptical, dielectric and elasto-mechanic behavior. Depending on whetherthe longitudinal axes of the molecules are oriented parallel orperpendicular to the two plates of a capacitor, the latter has adifferent capacitance; therefore the dielectric constant ε of the liquidcrystal differs in size for the two orientations. Substances whosedielectric constant is larger when the longitudinal axes of themolecules are oriented perpendicular to the capacitator plates arecalled dielectrically positive. Most liquid crystals used inconventional displays belong to this group.

[0004] The dielectric anisotropy is influenced both by thepolarizability of the molecule and permanent dipole moments. Onapplication of a voltage across the display, the longitudinal axis ofthe molecules is oriented such that the larger of the dielectricconstants comes into effect. The strength of interaction with theelectric field depends on the difference between the two constants. Whenthe difference is small, higher switching voltages are required thanwhen the difference is large. A wide range of operating volt-ages can berealized by introducing suitable polar groups such as nitrites (CN-) orfluorine into the liquid-crystal molecules.

[0005] In the liquid-crystalline molecules used in conventionalliquid-crystal displays, the dipole moment along the longitudinal axisof the molecule is larger than the dipole moment perpendicular to thelongitudinal axis of the molecule. The orientation of the larger dipolemoment along the longitudinal axis of the molecule likewise determinesthe orientation of the molecule in a liquid-crystal display in thefield-off state. In the most commonly used TN (twisted nematic) cells, aliquid-crystalline layer having a thickness of only 5 to 10 μm isinterposed between two plane glass plates each of which has been coatedby vapor deposition with an electrically conducting, transparent layerof tin oxide or indium-tin oxide as electrode. Between these films andthe liquid-crystalline layer there is a likewise transparent alignmentlayer which is usually made of plastic (e.g. polyimides). Due to surfaceforces, this layer forces the longitudinal axes of adjacent crystallinemolecules into a preferential direction such that, in the voltage-freecase, they rest on the inside of the display surface uniformly and havethe same orientation, either planar or having the same low tilt angle.Two polarizing films through which only linearly polarized light canpass are adhered to the outside of the display in specific arrangements.

[0006] Very efficient displays have been developed using liquid crystalsin which the larger dipole moment is parallel to the longitudinal axisof the molecule. Mostly, mixtures of 5 to 20 components are used toachieve a sufficiently broad mesophase temperature range, short responsetimes and low threshold voltages. However, difficulties are still causedby the high viewing angle dependence in liquid-crystal displays as used,for example, for laptops. Optimum image quality can be achieved when thedisplay surface is perpendicular to the viewing direction of theobserver. If the display is tilted relative to the viewing direction,image quality may deteriorate dramatically. To achieve a higher comfort,efforts are made to make the angle by which the display can be tiltedaway from the viewing angle of an observer as large as possible.Recently attempts have been made to improve the viewing angle dependenceby using liquid-crystalline compounds whose dipole moment perpendicularto the longitudinal axis of the molecule is larger than that parallel tothe longitudinal axis of the molecule. In the field-off state, thesemolecules are thus aligned perpendicular to the treated or coated glasssurface of the display. This lead to an improvement in the viewing angledependence. Such displays are called VA (vertical align) TFT displays.

[0007] There is still considerable scope for development in the field ofliquid-crystalline materials. Continuous attempts are being made toimprove the properties of liquid-crystalline display elements bydeveloping novel compounds which make it possible to optimize suchdisplays.

[0008] It is therefore an object of the invention to provideliquid-crystalline compounds having advantageous properties.

[0009] This object is achieved by compounds of the formula (Ia) or (Ib)

[0010] in which:

[0011] R, in each case independently of one another, is an alkyl oralkoxy radical having 1 to 12 carbon atoms which is unsubstituted,monosubstituted by —CF₃ or at least monosubstituted by halogen, anoxaalkyl, alkenyl or alkenyloxy radical having 2 to 12 carbon atoms oran oxaalkenyl radical having 3 to 12 carbon atoms, where one or more CH₂groups in these radicals may also, in each case independently of oneanother, be replaced by —O—, —S—, —CO—, —COO—, —OCO— or —OCO—O— in sucha way that heteroatoms are not linked directly to one another,

[0012] A, in each case independently of one another, is 1,4-phenylene,in which ═CH— may be replaced once or twice by ═N— and which may bemono- to tetrasubstituted, independently of one another, by halogen (—F,—Cl, —Br, —I), —CN, —CH₃, —CH₂F, —CHF₂, —CF₃, —OCH₃, —OCH₂F, —OCHF₂ or—OCF₃, 1,4-cyclohexylene, 1,4-cyclohexenylene or 1,4-cyclohexadienylene,in which —CH₂— may be replaced once or twice by, independently of oneanother, —O— or —S— and which may be mono- or polysubstituted byhalogen,

[0013] Z, in each case independently of one another, is a single bond, a—CH₂—CH₂—, —CF₂CF₂—, —CH═CH—, —CF═CH—, —CH═CF—, —C≡C—, —CO—O—, —O—CO—,—O—CH₂—, —CH₂—O—, O—CF₂— or a —CF₂—O— group,

[0014] X is —H, —F, —Cl, —CN, —NCS, —CF₃, —OCF₃, —OCHF₂,

[0015] Y, V are each, independently of one another, hydrogen, an alkyl,alkoxy, alkenyl or alkinyl radical having 1 to 15 or, respectively, 2bis 15 carbon atoms which is unsubstituted, monosubstituted by —CF₃ orat least monosubstituted by halogen where one or more CH₂ groups inthese radicals may also, in each case independently of one another, bereplaced by —O—, —S—, —CO—, —COO—, —OCO— or —OCO—O— in such a way thatheteroatoms are not linked directly to one another,

[0016] Y is additionally —F or —Cl,

[0017] W, in each case independently of one another, is —O—, —C(O)—,—CHF— or —CF₂— or —CH═ or —CF═ and, in formula (Ib), additionally —CH₂—

[0018] n, m are each, independently of one another, 0, 1, 2, 3 or 4 andthe dotted line is a single bond or a double bond,

[0019] with the proviso that X in formula (Ib)≠H when W is twice —CH₂—.In the general formulae (Ia) and (Ib), A is in each case independentlyof one another preferably unsubstituted or substituted 1,4-phenylene,unsubstituted or substituted 1,4-cyclohexylene, in which —CH₂— may bereplaced once or twice by —O—, or unsubstituted or substituted1,4-cyclohexenylene.

[0020] Particularly preferably, A is in each case independently of oneanother

[0021] R, Y and V in the general formulae (Ia) and (Ib) may each,independently of one another, be an alkyl radical and/or an alkoxyradical having 1 to 15 carbon atoms which can be straight-chain orbranched. It is preferably straight-chain, has 1, 2, 3, 4, 5, 6 or 7carbon atoms and accordingly is preferably methyl, ethyl, propyl, butyl,pentyl, hexyl, heptyl, methoxy, ethoxy, propoxy, butoxy, pentoxy hexoxyor heptoxy.

[0022] R, Y and V can each, independently of one another, be oxaalkyl,preferably straight-chain 2-oxapropyl (═methoxymethyl),2-(═ethoxymethyl) or 3-oxabutyl (═2-methoxyethyl), 2-, 3- or4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl.

[0023] R, Y and W can each, independently of one another, be an alkenylradical having 2-15 carbon atoms which can be straight-chain orbranched. It is preferably straight-chain and has 2 to 7 carbon atoms.Accordingly, it is in particular vinyl, prop-1- or prop-2-enyl, but-1-,-2- or but-3-enyl, pent-1-, -2-, -3- or pent4-enyl, hex-1-, -2-, -3-, 4-or hex-5-enyl, hept-1-, -2-, -3-4-, -5- or hept-6-enyl.

[0024] R, Y and V can each, independently of one another, be an alkylradical having 1 to 15 carbon atoms in which one CH₂ group has beenreplaced by —O— and one has been replaced by —CO—, these beingpreferably adjacent. These thus contain an acyloxy group —CO—O— or anoxycarbonyl group —O—CO—. These are preferably straight-chain and have 2to 6 carbon atoms.

[0025] R, Y and V can each, independently of one another, be an alkylradical having 1 to 15 carbon atoms in which one CH₂ group has beenreplaced by unsubstituted or substituted —CH═CH— and an adjacent CH₂group has been replaced by —CO— or —CO—O— or —O—CO—, in which case thiscan be straight-chain or branched. It is preferably straight-chain andhas 4 to 13 carbon atoms.

[0026] R, Y and V can each, independently of one another, be an alkylradical having 1 to 15 carbon atoms or an alkenyl radical having 2 to 15carbon atoms which is monosubstituted by —CN or —CF₃, these radicalsbeing preferably straight-chain. The substitution by —CN or —CF₃ is inany position.

[0027] R, Y and V can each, independently of one another, be an alkylradical having 1 to 15 carbon atoms or an alkenyl radical having 2 to 15carbon atoms which is at least monosubstituted by halogen, this radicalbeing preferably straight-chain and halogen is preferably —F or —Cl. Inthe case of polysubstitution, halogen being preferably —F. The resultingradicals also include perfluorinated radicals. In the case ofmonosubstitution, the fluoro or chloro substituent can be in any desiredposition, but is preferably in the ω-position.

[0028] R, Y and V can each, independently of one another, be an alkylradical in which two or more CH₂ groups are replaced by —O— and/or—CO—O—, in which case this radical can be straight chain or branched. Itis preferably branched and has 3 to 12 carbon atoms.

[0029] R, Y and V in the general formulae (Ia) and (Ib) are preferablyhydrogen or an alkyl radical, alkoxy radical or alkenyl radical having 1to 7 or, respectively, 2 to 7 carbon atoms.

[0030] Y is additionally preferably —F or —Cl, in particular —F.

[0031] Preferred indanes of the general formula (Ia) or (Ib) contain oneor two A cycles.

[0032] The compounds have a negative Δε and are therefore suitable foruse in VA TFT displays. They exhibit a very good compatibility with theusual substances used in liquid-crystal mixtures for displays.

[0033] The substituents X and W in the indane skeleton generates adipole moment perpendicular to the longitudinal axis of the moleculewhich may be increased, if desired, by suitable substituents in thependant moieties ZAZAR. In the field-off state, the compounds of theformulae (Ia) or (Ib) orientate such that their longitudinal axis of themolecule is perpendicular to the glass surface of a display.

[0034] The following groups of compounds, in which W, V, A, Y, Z, R, nand m are as defined above, were found to be particularly suitable.

[0035] The following compounds are especially suitable:

where R A Z V n-Alkyl

— H n-Alkyl

— n-Alkyl n-Alkyl

— —O-n-Alkyl n-Alkyl

—CH₂—CH₂— H n-Alkyl

—CH₂—CH₂— n-Alkyl n-Alkyl

—CH₂—CH₂— —O-n-Alkyl n-Alkyl

— H n-Alkyl

— n-Alkyl n-Alkyl

— —O-n-Alkyl n-Alkyl

—CH₂—CH₂— H n-Alkyl

—CH₂—CH₂— n-Alkyl n-Alkyl

—CH₂—CH₂— —O-n-Alkyl n-Alkyl

— H n-Alkyl

— n-Alkyl n-Alkyl

— —O-n-Alkyl n-Alkyl

—CH₂—CH₂— H n-Alkyl

—CH₂—CH₂— n-Alkyl n-Alkyl

—CH₂—CH₂— —O-n-Alkyl n-Alkyl

— H n-Alkyl

— n-Alkyl n-Alkyl

— —O-n-Alkyl n-Alkyl

—CH₂—CH₂— H n-Alkyl

—CH₂—CH₂— n-Alkyl n-Alkyl

—CH₂—CH₂— —O-n-Alkyl n-Alkyl

— H n-Alkyl

— n-Alkyl n-Alkyl

— —O-n-Alkyl n-Alkyl

—CH₂—CH₂— H n-Alkyl

—CH₂—CH₂— n-Alkyl n-Alkyl

—CH₂—CH₂— —O-n-Alkyl n-Alkyl

—CH₂—O— H n-Alkyl

—CH₂—O— n-Alkyl n-Alkyl

—CH₂—O— —O-n-Alkyl n-Alkyl

—O—CH₂— H n-Alkyl

—O—CH₂— n-Alkyl n-Alkyl

—O—CH₂— —O-n-Alkyl n-Alkyl

—CH₂—O— H n-Alkyl

—CH₂—O— n-Alkyl n-Alkyl

—CH₂—O— —O-n-Alkyl n-Alkyl

—O—CH₂— H n-Alkyl

—O—CH₂— n-Alkyl n-Alkyl

—O—CH₂— —O-n-Alkyl n-Alkyl

—O—CH₂— H n-Alkyl

—O—CH₂— n-Alkyl n-Alkyl

—O—CH₂— —O-n-Alkyl n-Alkyl

— H n-Alkyl

— n-Alkyl n-Alkyl

— —O-n-Alkyl n-Alkyl

—CH₂—CH₂— H n-Alkyl

—CH₂—CH₂— n-Alkyl n-Alkyl

—CH₂—CH₂— —O-n-Alkyl n-Alkyl

— H n-Alkyl

— n-Alkyl n-Alkyl

— —O-n-Alkyl n-Alkyl

—CH₂—CH₂— H n-Alkyl

—CH₂—CH₂— n-Alkyl n-Alkyl

—CH₂—CH₂— —O-n-Alkyl n-Alkyl-O—

— H n-Alkyl-O—

— n-Alkyl n-Alkyl-O—

— —O-n-Alkyl n-Alkyl

— H n-Alkyl

— n-Alkyl n-Alkyl

— —O-n-Alkyl n-Alkyl

— H n-Alkyl

— n-Alkyl n-Alkyl

— —O-n-Alkyl n-Alkyl

—CH₂—CH₂— H n-Alkyl

—CH₂—CH₂— n-Alkyl n-Alkyl

—CH₂—CH₂— —O-n-Alkyl n-Alkyl

— H n-Alkyl

— n-Alkyl n-Alkyl

— —O-n-Alkyl n-Alkyl-O—

— H n-Alkyl-O—

— n-Alkyl n-Alkyl-O—

— —O-n-Alkyl

where R A Z n-Alkyl

— n-Alkyl

—CH₂—CH₂— n-Alkyl

— n-Alkyl

—CH₂—CH₂— n-Alkyl

— n-Alkyl

—CH₂—CH₂— n-Alkyl

— n-Alkyl

—CH₂—CH₂— n-Alkyl

— n-Alkyl

—CH₂—CH₂— n-Alkyl

—CH₂—O— n-Alkyl

—O—CH₂— n-Alkyl

—CH₂—O— n-Alkyl

—O—CH₂— n-Alkyl

—O—CH₂— n-Alkyl

— n-Alkyl

—CH₂—CH₂— n-Alkyl

— n-Alkyl

—CH₂—CH₂— n-Alkyl-O

— n-Alkyl

— n-Alkyl

— n-Alkyl

—CH₂—CH₂— n-Alkyl

— n-Alkyl

—

[0036] The following structures are very particularly preferred:

[0037] From the last-mentioned-very-particularly preferred structures,those are especially preferred in which

[0038] n=1 and R=n-alkyl, in particular C₁-C₅-alkyl,

[0039] n=2 and R=n-alkyl, in particular C₁-C₅-alkyl,

[0040] n=1 and R=n-alkenyl, in particular vinyl, prop-1-enyl, but-1-enyland but-3-enyl,

[0041] n=2 and R=n-alkenyl, in particular vinyl, prop-1-enyl, but-1-enyland but-3-enyl.

[0042] The compounds of the formula (Ia) and (Ib) are prepared bymethods known per se, as described in the literature (for example in thestandard works, such as Houben-Weyl, Methoden der Organischen Chemie,Georg-Thieme-Verlag, Stuttgart), to be precise under reaction conditionswhich are known and suitable for said reactions. Use can also be madehere of variants which are known per se, but are not mentioned here ingreater detail.

[0043] If desired, the starting materials can also be formed in situsuch that they are not isolated from the reaction mixture butimmediately reacted further to give compounds of the formula (I) or(Ib).

[0044] An exemplary synthesis is shown below. By choosing appropriatestarting materials, the synthesis can be adapted to provide thecompounds of the (I) or (Ib) desired in each case.

[0045] 3-Bromofluorobenzene A, is reacted with the α, β-unsaturatedaldehyde B in the presence of lithium diisopropylamide to give thecompound C. In the presence of a palladium catalyst and oftriethylamine, this compound undergoes a ring closure reaction to givethe indanone D. D.

[0046] Fluorination of the keto compound D′ using a suitablefluorinating agent, such as DAST or SF₄, gives the difluoro compound E,from which hydrogen fluoride can be eliminated, if necessary using astrong base such as potassium tert-butylate, resulting in compound F. Atrifluoromethyl group can be introduced into the molecule by reactionwith F₃CSi(CH₃)₃ followed by treatment with KF/CH₃OH (G). Subsequentdehydration using SOCl₂/Pyridine gives compound H.

[0047] Alternatively, the indanone D′ can be reacted further as shown inFIG. 2a.

[0048] The keto compound D′ is reacted with propane-1,3-dithiol to givethe cyclic thioketal E′. Reaction with HF-pyridine in the presence ofdibromodimethylhydantoin already gives the end product H′ but also acertain amount of the bromide F′. The mixture is treated with base toeliminate HBr from compound F′ which gives compound G′. Compound G′ isthen hydrogenated in the mixture of G′ and H′ to give the end productH′.

[0049] Further possibilites for forming the indane skeleton are shown inFIG. 3.

[0050] A suitably substituted iodobenzene derivative J is firstdeprotonated at a low temperature using a strong base, such as LDA, andthen reacted wth a suitable acrolein derivative to give the alcohol K.Ring closure to give compound L is carried out by Heck reaction.

[0051] Benzofurans and dihydrobenzofurans according to the invention canbe prepared in accordance with the general reaction sequence shown inFIG. 4.

[0052] The starting phenol derivative M is first reacted with iodine inthe presence of a weak base to introduce an iodo group which givescompound N. Subsequent ring closure by reacting with a suitableacetylene derivative in the presence of a palladium(II) compound, suchas palladium(II) acetate, as catalyst produces the benzofuran derivativeO. The latter can be hydrogenated catalytically over palladium/carbon togive the dihydrobenzofuran derivative P.

[0053] Indacenes according to the invention can be obtained inaccordance with the reaction sequence shown in FIG. 5.

[0054] The starting 3,5-dibromofluorobenzene Q is reacted with theunsaturated aldehyde R in the presence of lithium diisopropylamide toobtain compound S. The latter undergoes ring closure to give theindanone T in the presence of a palladium catalyst and triethylamine.Following ketalization of the keto group using ethylene glycol in thepresence of toluenesulfonic acid, this process is repeated using theunsaturated aldehyde V to give the indacene X. Removal of the protectivegroup by means of an acid gives the diketone Y which can be convertedinto the end product Z by means of suitable fluorinating agents such asSF₄.

[0055] The reactions shown are to be construed as merely illustrative.The person skilled in the art can modify the above discussed synthesesappropriately and use other suitable synthetic routes so as to obtaincompounds of the formulae (Ia) and (Ib).

[0056] As mentioned above, the compounds of the formulae (Ia) and (Ib)can be used for producing liquid-crystalline mixtures. The inventiontherefore like-wise provides a liquid-crystalline medium comprising atleast two liquid-crystalline compounds including at least one compoundof the formulae (Ia) and (Ib).

[0057] The invention likewise provides liquid-crystalline mediacomprising 2 to 40, in particular 4 to 30, components as furtherconstituents besides one or more compounds of the formulae (Ia) and/or(Ib) according to the invention. These media very particularlypreferably comprise 7 to 25 components besides one or more compoundsaccording to the invention. These further constituents are preferablyselected from nematic or nematogenic (monotropic or isotropic)substances, in particular substances from the classes of theazoxybenzenes, benzylideneanilines, biphenyls, terphenyls, phenyl orcyclohexyl benzoates, phenyl or cyclohexyl esters ofcyclohexanecarboxylic acid, phenyl or cyclohexyl esters ofcyclohexylbenzoic acid, phenyl or cyclohexyl esters ofcyclohexylcyclohexanecarboxylic acid, cyclohexylphenyl esters of benzoicacid, of cyclohexanecarboxylic acid and ofcyclohexylcyclohexanecarboxylic acid, phenylcyclohexanes,cyclohexylbiphenyls, phenylcyclohexylcyclohexanes,cyclohexylcyclohexanes, cyclohexylcyclohexylcyclohexenes,1,4-bis-cyclohexylbenzenes, 4′,4′-bis-cyclohexylbiphenyls, phenyl- orcyclohexylpyrimidines, phenyl- or cyclohexylpyridines; phenyl- orcyclohexyldioxanes, phenyl- or cyclohexyl-1,3-dithianes,1,2-diphenylethanes, 1,2-dicyclohexylethanes,1-phenyl-2-cyclohexylethanes,1-cyclohexyl-2-(4-phenylcyclohexyl)ethanes,1-cyclohexyl-2-biphenylylethanes, 1-phenyl-2-cyclohexylphenylethanes,halogenated or non-halogenated stilbenes, benzyl phenyl ethers, tolansand substituted cinnamic acids. The 1,4-phenylene groups in thesecompounds may also be fluorinated.

[0058] The most important compounds suitable as further constituents ofmedia according to the invention can be characterized by the formulae(II), (III), (IV), (V) and (VI):

R′-L-E-R″  (II)

R′-L-COO-E-R″  (III)

R′-L-OOC-E-R″  (IV)

R′-L-CH₂CH₂-E-R″  (V)

R′-L-CF₂O-E-R″  (Vl)

[0059] In the formulae (II), (III), (IV), (V) and (VI), L and E, whichmay be identical or different, are in each case, independently of oneanother, a bivalent radical-from the group formed by -Phe-, -Cyc-,-Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -G-Phe- and -G-Cyc- andtheir mirror images, where Phe is unsubstituted or fluorine-substituted1,4-phenylene, Cyc is trans-1,4-cyclohexylene or 1,4-cyclohexylene, Pyris pyrimidine-2,5-diyl or pyridine-2,5-diyl, Dio is 1,3-dioxane-2,5-diyland G is 2-(trans-1,4-cyclohexyl)ethyl, pyrimidine-2,5-diyl,pyridine-2,5-diyl or 1,3-dioxane-2,5-diyl.

[0060] One of the radicals L and E is preferably Cyc or Phe. E ispreferably Cyc, Phe or Phe-Cyc. The media according to the inventionpreferably contain one or more components selected from the compounds ofthe formulae (II), (III), (IV), (V) and (VI) in which L and E areselected from the group consisting of Cyc and Phe and simultaneously oneor more components selected from the compounds of the formulae (II),(III), (IV), (V) and (VI) in which one of the radicals L and E isselected from the group consisting of Cyc and Phe and the other radicalis selected from the group consisting of -Phe-Phe-, -Phe-Cyc-,-Cyc-Cyc-, -G-Phe- and -G-Cyc-, and optionally one or more componentsselected from the compounds of the formulae (II), (III), (IV), (V) and(VI) in which the radicals L and E are selected from the groupconsisting of -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-.

[0061] In a smaller subgroup of the compounds of the formulae (II),(III), (IV), (V) and (VI), R′ and R″ are in each case, independently ofone another, alkyl, alkenyl, alkoxy, alkoxyalkyl, alkenyloxy oralkanoyloxy having up to 8 carbon atoms. This smaller subgroup isreferred to as group A below, and the compounds are labelled with thesubformulae (IIa), (IIIa), (IVa), (Va) and (Via). In most of thesecompounds, R′ and R″ are different from one another, one of theseradicals usually being alkyl, alkenyl, alkoxy or alkoxyalkyl.

[0062] In another smaller subgroup of the compounds of the formulae(II), (III), (IV), (V) and (VI) which is referred to as group B, E is

[0063] In the compounds of group B referred to using the subformulae(IIb), (IIIb), (IVb), (Vb) and (VIb), R′ and R″ are as defined for thecompounds of the subformulae (IIa) to (VIa) and are preferably alkyl,alkenyl, alkoxy or alkoxyalkyl.

[0064] In a further smaller subgroup of the compounds of the formulae(II), (III), (IV), (V) and (Vl), R″ is -CN; this subgroup is referred toas group C below, and the compounds of this subgroup are correspondinglydescribed by subformulae (IIc), (IIIc), (IVc), (Vc) and (VIc). In thecompounds of the subformulae (IIc), (IIIc), (IVc), (Vc) and (VIc), R′ isas defined for the compounds of the subformulae (IIa), (IIIa), (IVa),(Va) and (VIa) and is preferably alkyl, alkoxy or alkenyl.

[0065] In addition to the preferred compounds of groups A, B and C,other compounds of the formulae (II), (III), (IV), (V) and (VI) havingother variants of the proposed substituents are also customary. Allthese substances can be obtained by methods which are known from theliterature or analogously thereto.

[0066] Besides compounds of the formulae (Ia) and/or (Ib) according tothe invention, the media according to the invention preferably containone or more compounds selected from group A and/or group B and/or groupC. The proportions by weight of the compounds from these groups in themedia according to the invention are preferably Group A: 0 to 90%,preferably 20 to 90%, in particular 30 to 90% Group B: 0 to 80%,preferably 10 to 80%, in particular 10 to 70% Group C: 0 to 80%,preferably 5 to 80%, in particular 5 to 50%,

[0067] the sum of the proportions by weight of the group A and/or Band/or C compounds present in the particular media according to theinvention preferably being 5% to 90% and in particular 10% to 90%.

[0068] The media according to the invention preferably comprise 1 to40%, particularly preferably 5 to 30%, of compounds of the formulae (Ia)and/or (Ib) according to the invention. Further preferred media arethose which comprise more than 40%, in particular 45 to 90%, ofcompounds of the formulae (Ia) and/or (Ib) according to the invention.The media preferably comprise three, four or five compounds of theformulae (Ia) and/or (Ib) according to the invention.

[0069] Examples of the compounds of the formulae (II), (III), (IV), (V)and (VI) are the following compounds:

[0070] where R¹, R²=—C_(n)H_(2n+1) where n=1-8 and

[0071] L¹, L²=—H or —F,

[0072] where m, n=1-8.

[0073] The media according to the invention are prepared in a mannerwhich is customary per se. In general, the components are dissolved inone another, expediently at elevated temperature. By means of suitableadditives, the liquid-crystalline phases can be modified in accordancewith the invention in a manner such that they can be used in all typesof liquid-crystal display elements which have hitherto been disclosed.Additives of this type are known to those skilled in the art and aredescribed in detail in the literature (H. Kelker/R. Hatz, Handbook ofLiquid Crystals, Verlag Chemie, Weinheim, 1980). For example, pleochroicdyes can be added for the production of colored guest-host systems, orsubstances can be added to modify the dielectric anisotropy, theviscosity and/or the orientation of the nematic phases.

[0074] Because of their negative Δε, the compounds of the formula (I)are suitable for use in VA TFT displays. The invention thereforelikewise provides an electro-optical liquid-crystal display containing aliquid-crystalline medium according to the invention.

[0075] The examples below illustrate the invention:

EXAMPLES Synthetic Examples Example 1

[0076]1-(2-Fluoro-6-iodo-4-methyl-phenyl)-2-(4′-propylbicyclohexyl-4-yl)-prop-2-en-1-ol

[0077] An initial charge of 31.1 g (0.22 mol) of2,2,6,6-tetramethylpiperidine in 350 ml of tetrahydrofuran is cooleddown to −20° C. 135 ml of 1.6 M butyllithium in hexane (0.22 mol) areadded dropwise at this temperature. The mixture is cooled down to -18°C. and 47.2 g (0.2 mol) of 1-fluoro-3-iodo-5-methylbenzene are addeddropwise at this temperature. The reaction mixture is stirred foranother hour at −80° C. and then treated with 52.5 g (0.2 mol) of3-(4′-propylbicyclohexyl-4-yl)propenal. The mixture is allowed to warmto 0° C., hydrolyzed with water and diluted hydrochloric acid and thensubjected to conventional work-up.

[0078] Yield 75 g (75% of theory)

Example 2

[0079] 7-Fluoro-5-methyl-2-(4′-propylbicyclohexyl-4-yl)-indan-1-one

[0080] 75 g (0.15 mol) of1-(2-fluoro-6-iodo-4-methylphenyl)-2-(4′-propyl-bicyclohexyl-4-yl)-prop-2-en-1-ol,50 ml of triethylamine, 400 mg of palladium(II) acetate (1.8 mmol) and960 mg (3.7 mmol) of triphenylphosphine are dissolved in 200 ml ofacetonitrile and refluxed overnight. The mixture is cooled down to roomtemperature and subjected to conventional workup.

[0081] Yield 44.5 g (80% of theory)

Example 3

[0082] 14-Propyl-4′-(1,1,7-trifluoro-5-methylindan-2-yl)bicyclohexyl

[0083] 44.5 g (0.12 mol) of7-fluoro-5-methyl-2-(4′-propylbicyclohexyl-4-yl)indan-1-one aredissolved in 400 ml of dichloromethane and the solution is treated with32.4 g (0.3 mol) of SF₄ in an autoclave at room temperature. After thereaction has ended, the mixture is subjected to conventional work-up.

[0084] Yield 33.5 g (71% of theory)

Example 4

[0085] 4′-(3,4-Difluoro-6-methyl-1H-inden-2-yl)4-propylbicyclohexyl

[0086] 10.0 g (0.025 mol) of4-propyl-4′-(1,1,7-trifluoro-5-methylindan-2-yl)-bicyclohexyl arestirred together with 5.6 g of potassium tert-butylate in 200 ml oftetrahydrofuran at 60° C. for 6 hours. The mixture is then subjected toconventional work-up.

[0087] Yield 5.9 g (63% of theory)

Example 5

[0088]4′-(4-Fluoro-6-methyl-3-trifluoromethyl-1H-inden-2-yl)4-propylbicyclohexyl

[0089] 8.5 g (0.023 mol) of7-fluoro-5-methyl-2-(4′-propylbicyclohexyl-4-yl)-indan-1-one aredissolved in 50 ml of-tetrahydrofuran and the solution is cooled down to0° C. 3.7 ml (0.025 mol) of trifluoromethyltrimethylsilane are added.0.1 ml of tetrabutylammonium fluoride (1 M solution in THF) are added.After the reaction has ended, the mixture is subjected to conventionalworkup, and then the product is taken up in 40 ml of methanol, 200 mg ofpotassium fluoride are added and the mixture is refluxed for 10 hours.The resulting carbinol is dissolved in 30 ml of pyridine and 1.7 ml(0.024 mol) of thionyl chloride are added dropwise. The mixture isstirred for 10 hours at room temperature and then subjected toconventional workup.

[0090] Yield 6.9 g (71% of theory)

Example 6

[0091] 2-lodo-4-methyl-6-fluorophenol

[0092] 55.5 g (0.44 mol) of 2-fluoro-4-methylphenol and 120.3 g (0.87mol) of potassium carbonate are dissolved in 275 ml of water and thesolution is cooled down to 5° C. 127.5 g of iodine (0.5 mol) are addedin portions.

[0093] After the reaction has ended, the mixture is subjected toconventional work-up.

[0094] Yield 86.5 g (78% of theory)

Example 7

[0095] 7-Fluoro-5-methyl-2-(4′-propylbicyclohexyl-4-yl)-benzofuran

[0096] 46.5 g (0.2 mol) of 4′-propylbicyclohexylacetylene, dissolved indimethyl-formamide, are added dropwise to an initial charge of 50.5 g(0.2 mol) of 2-iodo-4-methyl-6-fluorophenol, 4.2 g (6 mmol) ofbis(triphenylphosphine)-palladium(II) chloride, 1.2 g (6.3 mmol) ofcopper(l) iodide and 40.5 g (0.4 mol) of triethylamine in 200 ml ofdimethylformamide at room temperature. The mixture is stirred for onehour at room temperature and for 2 hours at 40° C. and then subjected toconventional workup.

[0097] Yield 38.5 g (54% of theory)

[0098] The compound can be converted into the dihydrobenzofuran byhydro-genation under atmospheric pressure using palladium-on-carbon(10%).

Example 8

[0099]

[0100] An initial charge of 41.0 ml of a 2 molar solution of lithiumdiisopropylamide in cyclohexane/ethylbenzene/tetrahydrofuran (79.612mmol) and 150 ml of THF is treated with 60.3 g (93.143 mmol) of1-bromo-3-fluorobenzene in 20 ml of THF at −74° C. The mixture isstirred for 1 hour followed by addition of a solution of 18.4 g (70.111mmol) of a in 40 ml of THF. The mixture is stirred for 12 hours,acidified with 1 n HCI and extracted with methyl t-butyl ether. Theorganic phase is dried and evaporated and the product is crystallizedfrom n-hexane.

[0101] Yield 25.9 g (84.4% of theory)

Example 9

[0102]

[0103] 95.8 g (58.98 mmol) of b are dissolved in a warm mixture of 185ml of ace-tonitrile and 40 ml of triethylamine. 2.5 g (2.538 mmol) ofbis-(tri-o-tolylphosphine)palladium(II) chloride catalyst are added tothis solution. The mixture is heated to 90° C. under nitrogen and thensubjected to con-ventional work-up. Crystallization from hexane yields16.2 g of c.

[0104] Yield 16.2 g (77.0% of theory)

Example 10

[0105]

[0106] 5.9 g (16.548 mmol) of c and 3.207 ml (32.0 mmol) of1,3-propanedithiol are dissolved in 50 ml of dichloromethane. 10 ml(79.617 mmol) of boron trifluoride diethylether complex are added tothis solution at −10° C. The mixture is stirred at −5 to −10° C. andthen allowed to warm to room temperature overnight. The product solutionis poured over bicarbonate and the mixture is stirred until gasevolution has ceased. The mixture is extracted twice withdichloromethane, dried and chromatographed using a methyl t-butylether/heptane mixture (1:10). 232PC

Example 11

[0107]

[0108] An initial charge of 41 ml of a 65% strength hydrogen fluoridesolution in pyridine and 11.4 g (39.87 mmol) of1,3-dibromo-5,5-dimethylhydantoin in 35 ml of dichloromethane is cooleddown to −75° C. 4.1 g (9.178 mmol) of d in 25 ml of dichloromethane areadded to this solution. The cooling bath is removed and the reactionmixture is stirred overnight. 200 ml of ice-cooled sodium bisulfitesolution and 500 ml of 2 n NaOH are added. The aqueous phase isextracted three times with dichloromethane and the organic phase iswashed with saturated sodium chloride solution, dried and evapo-rated.The product is chromatographed using diethyl ether/heptane (1:20).

Example 12

[0109]

[0110] 8 ml of diazabicyclo[5.4.0]undec-7-ene in 8 ml of THF are addedto 4.20 g of the raw product from Example 12. The mixture is stirred atroom temperature until the reaction is complete (TLC). The mixture isthen evaporated, the residue is taken up in water and dichloromethane,extracted, dried and chromatographed using hexane.

Example 13

[0111]

[0112] 2.3 g of the raw product from Example 12 are hydrogenated over1.8 g of 5% palladium on carbon in 30 ml of tetrahydrofuran.

[0113] The following compounds are obtained in analogy to Examples 8-13:

Phases: K 122 I Cl.p.: 23.7° C. Δε: −8.5 Δn: 0.075

Phases: K 99 I Cl.p.: 18.1° C. Δε: −7.1 Δn: 0.086

Phases: K 118 I Cl.p.: 50.5° C. Δε: −11.4 Δn: 0.065

Phases: K 134 I Cl.p.: 104.3° C. Δε: −11.7 Δn: 0.0775

Phases: K 105 I Cl.p.: 77.7° C. Δε: −8.2 Δn: 0.077

Phases: K 171 SmB (170) N (170.7) I Cl.p.: 180.5° C. Δε: −5.4 Δn: 0.0754

Phases: K 130 SmB 168 N 203.7 I Cl.p.: 202.3° C. Δε: −8.3 Δn: 0.075

Phases: K 109 SmA-1 156 SmA-2 183 N 220.7 I Cl.p.: 253.5° C. Δε: −6.7Δn: 0.087

Phases: K 110 SmA-1 168 SmA-2 171 N 207.0 I Cl.p.: 233.3° C. Δε: −5.6Δn: 0.0765

[0114] Hereinbefore, cl.p. denotes the clearing point, Δn denotes thedielectric anisotropy and Δn denotes the birefringence.

Mixture Examples

[0115] The following abbreviations are used:

[0116] Furthermore:

[0117] cI.p. denotes the clearing point [° C.]

[0118] Δn denotes the optical anisotropy (birefringence) at 20° C. and589 nm

[0119] Δε denotes the dielectric anisotropy at 20° C. and 1 kHz

[0120] ε_(∥)denotes the dielectric constant parallel to the director at20° C. and 1 kHz

[0121] K₃/K₁ denotes the ratio of the elastic constants K₃ and K₁

[0122] γ₁ denotes the rotational viscosity [mPa·s] (at 20 C. unlessstated otherwise)

[0123] V₀ denotes the capacitive threshold voltage [V]

[0124] The capacitive threshold voltage is measured using a displayhaving two plane-parallel outer plates at a separation of 20 μm andelectrode layers covered by rubbed polyimide alignment layers on theinsides of the outer plates which produce a homeotropic edge alignmentof the liquid crystal molecules.

[0125] The polymerizable compounds are polymerized in the display by UVirradiation at 28 mW/cm² and for about 2 minutes, simultaneouslyapplying a voltage of 10 V across the display.

[0126] The following liquid-crystal mixtures were prepared and used todetermine the values below.

Example 14

[0127] CY-3-O2 20.00% Cl.p. +74.0 CY-5-O2 11.00% Δn 0.0813 CCY-3-O310.00% Δε −3.9 CCY-4-O2 10.00% ε_(∥) 3.7 CPY-2-O2 7.00% K₃/K₁ 1.04CC-5-V 20.00% γ₁ 109 CC-3-V1 12.00% V₀ 2.02 CCH-35 5.00% IND 5.00%

Example 15

[0128] CY-3-O2 12.00% Cl.p. +75.0 CY-5-O2 12.00% Δn 0.0823 CCY-4-O27.00% Δε −3.2 CPY-2-O2 12.00% ε_(∥) 3.5 CPY-3-O2 3.00% K₃/K₁ 0.97 CC-5-V20.00% γ₁ 91 CC-3-V1 12.00% V₀ 2.17 CC-4-V 10.00% CCH-35 4.00% IND 8.00%

1. Indanes having negative Δε of the formula (Ia) or (Ib)

in which: R, in each case independently of one another, is an alkyl oralkoxy radical having 1 to 12 carbon atoms which is unsubstituted,monosubstituted by —CF₃ or at least monosubstituted by halogen, anoxaalkyl, alkenyl or alkenyloxy radical having 2 to 12 carbon atoms oran oxaalkenyl radical having 3 to 12 carbon atoms, where one or more CH₂groups in these radicals may also, in each case independently of oneanother, be replaced by —O—, —S—, —CO—, —COO—, —OCO— or —OCO—O— in sucha way that heteroatoms are not linked directly to one another, A, ineach case independently of one another, is 1,4-phenylene, in which ═CH—may be replaced once or twice by ═N— and which may be mono- totetrasubstituted, independently of one another, by halogen (—F, —Cl,—Br, —I), —CN, —CH₃, —CH₂F, —CHF₂, —CF₃, —OCH₃, —OCH₂F, —OCHF₂ or —OCF₃,1,4-cyclohexylene, 1,4-cyclohexenylene or 1,4-cyclohexadienylene, inwhich —CH₂— may be replaced once or twice by, independently of oneanother, —O— or —S— and which may be mono- or polysubstituted byhalogen, Z, in each case independently of one another, is a single bond,a —CH₂—CH₂—, —CF₂CF₂—, —CH═CH—, —CF═CH—, —CH═CF—, —C═C—, —CO—O—, —O—CO—,—O—CH₂—, —CH₂—O—, O—CF₂— or a—CF₂—O— group, X is —H, —F, —Cl, —CN, —NCS,—CF₃, —OCF₃, —OCHF₂, Y, V are each, independently of one another,hydrogen, an alkyl, alkoxy, alkenyl or alkinyl radical having 1 to 15or, respectively, 2 bis 15 carbon atoms which is unsubstituted,mono-substituted by —CF₃ or at least monosubstituted by halogen whereone or more CH₂ groups in these radicals may also, in each caseindependently of one another, be replaced by —O—, —S—, —CO—, —COO—,—OCO— or —OCO—O— in such a way that heteroatoms are not linked directlyto one another, Y is additionally —F or —Cl, W, in each caseindependently of one another, is —O—, —C(O)—, —CHF— or —CF₂— or —CH═ or—CF═ and, in formula (Ib), addition-ally —CH₂— n, m are each,independently of one another, 0, 1, 2, 3 or 4 and the dofted line is asingle bond or a double bond, with the proviso that X in formula (Ib)≠Hwhen W is twice —CH₂—.
 2. Indanes as claimed in claim 1:


3. Indanes as claimed in claim 1:


4. Liquid-crystalline medium comprising at least two liquid-crystallinecompounds including at least one compound of the formula (I). 5.Electro-optical liquid-crystal display containing a liquid-crystallinemedium as claimed in claim 4.